Swelling tests tensile properties

Swelling tests and determination of tensile properties. The procedure for estimating cross-link density from equilibrium swelling data is described in detail in a previous paper (6). The tensile properties of the PU films were carried out at 23°C and 60% relative humidity. The crosshead speed and distance were 10 mm/min and 30 mm, respectively. A more detailed description of the tensile tests is given elsewhere (6). 

Tests for scorch and rate of cure should be distinguished from tests for degree of cure or optimum cure measured on the vulcanised material. The latter type of test estimates degree of cure by measuring the physical properties of test pieces vulcanised for various times, tensile properties, swelling and set measurements being the parameters most commonly used. 

Three tensile bars and two volume change specimens of each elastomer were exposed In a test tube to each of the pure fuels and the mixtures. Exposure for 72 hours at room temperature was determined to be sufficient for most elastomers to approach equilibrium swell. Tensile properties were determined using the ASTM D412 procedure for original samples and fuel exposed samples Immediately after removal from the fuel. Swell measurements were conducted per the ASTM D471 procedure. To obtain the amount of extractables the fuel swelled samples were dried In a vacuum oven at 100°C for 24 hours and then weighed. In most samples constant weight was achieved within this time period. 

Samples were cured from each of the three compounds and then a large numher of physical and chemical properties were examined, including tensile properties, tear strength, resilience, abrasion resistance, ageing, and performance and swelling in test fluids. The results revealed that the abrasion volume of blends of virgin NR and the Novel reclaim is lower than that of the Control reclaim and comparable to the Control NR. Although the tensile properties of the Novel reclaim were found to be lower than Control NR, the workers concluded that they would be acceptable for a tyre tread application and overall it was concluded that the 85 15 Novel reclaim product could be used as an alternative to both the other two compounds for tyre tread manufacture. 

For quality cured thermoset resins, approximately one percent of the mass is soluble when subjected to long-term leaching with tetrahydrofuran. Equilibrium is approached in two weeks resin swell is not visually noticeable. The monomeric, chemical structures are such that the hydrocarbon resins exhibit more pronounced viscoelastic properties whereas, the epoxy resins are similar to elastic bodies when subjected to tensile testing at room temperature. Therein, LRF 216 is less sensitive to flaws and is more nonlinear in tensile or compressive stress-strain analysis. 

Following are some properties of AECP explosion /emp(PA method) 305—10°(5 sec) impact test with 2kg wt—detonated at 12" bygroscopicity(% gain in wt at RT and 77% RH) 23% after 6 days and 22.3% after 13 days thermal stability—relatively stable at 85° for long periods of time but decomp extensively at 125° within a week tensile strength—decreases with increase in perchlorate content solubility—insol in common solvents, sometimes dissolved at elevated temps with decompn, swelled in some polar liquids dissociated to some extent in HaO compatibility with NC—incompatible... 

To relate the physical properties of carbon black to rubber properties, we tested these tread blacks in the ASTM natural rubber recipe and in an SBR 1500 test recipe. In both elastomers, we checked standard stress/strain properties of modulus, tensile strength, and hardness. In the natural rubber recipe we also tested Firestone running temperature and rebound, and Goodyear rebound. In the SBR we checked percent swell, extrusion rate, viscosity, and laboratory abrasion. 

Practically, tensile samples were allowed to swell in Millipore water for 24h in order to reach the equilibrium prior mechanical testing. In such conditions, only strain due to mechanical deformation, and not to swelling process, was measured. Figure 11 presents typical true stress-strain curves. It comes out that the introduction of PCL segments enliances the overall mechanical properties in comparison to the PDMAEMA hydrogel. 

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